blown amp - vintage speaker the culprit?

Calling on the collective experience/ knowledge, here:

A while ago, i was given a pair of vintage speakers. They appeared to be working without issue at the gentleman's house and seemed to work fine for a while at home as well.

After a bit of listening a couple of nights ago, I noticed some distortion in the right channel. It seemed intermittent at first, but gradually worsened.

In an attempt to determine if it was the speaker or the amp that was the problem, i powered down and unplugged the unit to swap speakers left and right (to see if the problem stayed in the right channel, which would make it an amp or source problem - or if it moved to the left - speaker problem). When i connected everything and powered up again,I heard a loud buzz come from the amp for about 4-5 seconds, after which it clicked on to 'ready'. However, now the right channel was dead. I tested the left channel; working fine with both speakers.
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While at an audio store in Toronto today, the owner of the store suggested that it could have potentially blown because of a faulty speaker (eg. caps are toast/ issues with crossover etc).

Although I understand that a speaker's sound quality can diminish over time, I was never under any impression that a speaker can blow an amp (provided the amp and speaker were a good match in the first place and in proper working order).

Is this true? can speakers that are out of spec cause an amp to blow?

NOTE: the amp in question appeared to have a slight problem developing with the power-on safety relay even before connecting the vintage speakers, whereupon it began to develop a loud hum/ buzz (emanating from the amp itself) before clicking into 'ready' mode. I mention this b/c I believe the blown channel likely does not have anything to do with the speaker, but i would like to hear what you guys have to say on the subject.

(pairing is Sugden A48B amp with epi100's)